The aim of this project is to elucidate the inheritance of different sperm abnormalities found in the BALB/cJ and PL/J mouse strains. Reciprocal crosses between the strains BALB/cJ and DBA/2J, as well as between BALB/cJ and PL/J, were performed. In addition, a wide range of backcrosses were completed. The unveiling of the complex results in a blind evaluation of coded slides is still underway in the Statistics Branch.